Cooling fan

ABSTRACT

A cooling fan for cooling a heat source includes a frame ( 10 ), a stator ( 20 ) mounted in the frame, a rotor ( 30 ) rotatably attached in the frame, a cover ( 40 ) fixed on the frame, and a pair of bearings ( 50, 60 ) received in the cover and the frame respectively. The rotor includes an impeller and a shaft ( 36 ) inserted through the impeller, wherein the shaft has an upper portion being received in one of the pair of bearings in the cover, and a lower portion being received in another one of the pair of bearing in the frame; thus, a vibration of the shaft can be prevented by supports of the pair of bearings, and the rotor is able to maintain a stable rotation, as the cooling fan is in a high speed operation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cooling fan, and more particularly toa cooling fan having a pair of bearings for providing a stable operationto the cooling fan.

2. Description of Related Art

With continuing development of the electronic technology, electroniccomponents such as CPUs generate more and more heat that is required tobe dissipated immediately. A heat sink is often mounted on theelectronic component for absorbing heat therefrom, and a fan is alsoprovided to further remove heat from the heat sink with its forcedairflow.

Conventionally, the fan includes a frame, a stator attached in theframe, a bearing received in the stator, and a rotor rotatably mountedto the stator. The rotor includes an impeller and a shaft extendingdownwardly from the impeller, wherein a lower portion of the shaft isenclosed by the bearing. When the fan operates, the impeller is rotatedaround the shaft with a support provided by the bearing.

However, the shaft only has the lower portion received in the bearing,while an upper portion thereof is not supported by any structure, whichleads the impeller fixed on a upper portion of the shaft is prone toperform a vibration when the impeller is in a high speed rotation. Thisvibration would cause the fan to have an unstable operation that maygenerate a noise and reduce a lifetime of the fan.

What is needed, therefore, is a heat dissipating device which canovercome the above-mentioned disadvantages.

SUMMARY OF THE INVENTION

A cooling fan for cooling a heat source includes a frame, a statormounted in the frame, a rotor rotatably attached in the frame, a coverfixed on the frame, and a pair of bearings received in the cover and theframe respectively. The rotor includes a impeller and a shaft insertedthrough the impeller, wherein the shaft has an upper portion beingreceived in one of the pair of bearings in the cover, and a lowerportion being received in another one of the pair of bearing in theframe; thus, a vibration of the shaft can be prevented by supports ofthe pair of bearings, and the rotor is able to maintain a stablerotation, when the cooling fan is in a high speed operation.

Other advantages and novel features of the present invention will becomemore apparent from the following detailed description when taken inconjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present apparatus can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the present apparatus. Moreover,in the drawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a view of a vertical section of a cooling fan in accordancewith a preferred embodiment of the present invention;

FIG. 2 is an isometric view of a cover of the cooling fan of FIG. 1; and

FIG. 3 is an isometric view of the cooling fan of FIG. 1 with the coverbeing removed for clarity.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a cooling fan in accordance with a preferredembodiment of the present invention for cooling a heat source (notshown), comprises a frame 10, a stator 20 disposed in the frame 10, arotor 30 rotatably installed on the stator 20, a cover 40 secured on theframe 10 to cover the stator 20 and the rotor 30, and a pair of bearings50, 60 respectively contained in a bottom of the frame 10 and in thecover 40.

Referring to FIGS. 1 and 3, the frame 10 is used for being fixed on astructure (not shown) for mounting the cooling fan thereon. The frame 10comprises a square lower plate 12, a square upper plate 14 parallel tothe lower plate 12, and an annular sidewall 16 sandwiched between andinterconnecting the lower plate 12 and the upper plate 14. Each of theupper plate 14 and the lower plate 12 has four circular holes 120, 140defined in four corners thereof respectively. Four grooves 142 aredefined near the four circular holes 140 of the upper plate 14respectively, each of which defines a threaded hole 1420 at a bottomface thereof. A circular through hole 18 is defined through the upperplate 14 and the lower plate 12 for forming a cylindrical space toreceive the stator 20 and the rotor 30 therein. A collar 122 is formedin a central area of a bottom of the through hole 18 with a plurality ofribs 123 extending outwardly and radially from a circumferentialperiphery of the collar 122 to connect with the sidewall 16, therebysecuring the collar 122 to the sidewall 16. The collar 122 has a hollowtube 124 extending upwardly and perpendicularly from a center area of atop face thereof for accommodating a lower one, in this embodiment, thebearing 50 of the pair of bearings 50, 60 therein. An annular wall 126is formed outwardly and horizontally around a lower portion of the tube124. An annulus 128 extends inwardly and vertically from an inner faceof the tube 124 and opposite to the annular wall 126.

The pair of bearings 50, 60 can be oil-containing bearings, or ballbearings. The lower bearing 50 of the pair of bearings 50, 60 isreceived in the tube 124 of the frame 10 in such a manner that a bottomface of the lower bearing 50 of the pair of bearings 50, 60 contacts atop face of the annulus 128 on the tube 124, and an outer face of thelower bearing 50 contacts the inner face of the tube 124. The lowerbearing 50 of the pair of bearings 50, 60 defines a cylindrical passage(not labeled) therein, which is located coaxially with the tube 124.

The stator 20 is disposed in the frame 10 and comprises a circular base22 contacting a top face of the annular wall 126, and a plurality ofcoils 24 installed on the base 22 for exerting an alternating magnetfield when an alternating current is given to the stator 20. The base 22defines a hole (not labeled) therein to enable the stator 20 to besleeved onto the tube 124.

The rotor 30 is received in the through hole 18 of the frame 10. Therotor 30 comprises a hub 32, a permanent magnetic sleeve 38 installedinto the hub 32, a plurality of blades 34 extending radially andoutwardly from a circumference of the hub 32, and a shaft 36 insertedthrough the hub 32. The hub 32 comprises a disk (not labeled) and anannular flange (not labeled) extending downwardly and perpendicularlyfrom a rim of the disk. A central area of a top face of the disk isconcaved to form a cavity 320 in the hub 32. The shaft 36 is insertedthrough a center of the disk of the hub 32 with an upper portion thereofextending beyond the center of the disk and partly exposed within thecavity 320; and a lower portion inserted into the passage of the lowerbearing 50 of the pair of bearings 50, 60 so as to be confined by thelower bearing 50 of the pair of bearings 50, 60, whereby the lowerportion of the shaft 36 is supported to be prevented from vibration. Theshaft 36 defines a recess (not labeled) near a bottom portion thereoffor being snapped by the annulus 128 of the frame 10, thus preventingthe rotor 30 from falling off from the frame 10. The magnetic sleeve 38has an annular configuration contacting an inner circumference of theflange of the hub 32, wherein the magnetic sleeve 38 surrounds the shaft36 and has a lower portion opposing to the coils 24 of the stator 20.

Also referring to FIG. 2, the cover 40 rests on the frame 10 to sandwichthe rotor 30 and the stator 20 with the frame 10. The cover 40 has fourstraight beams 42 connect with each other to construct a squareconfiguration therefor. A circular plate 44 is formed in a central areaof the cover 40 corresponding to the disk of the hub 32 in a manner suchthat the circular plate 44, the disk, and the collar 122 are inalignment with each other. Four beams 48 connect the circular plate 44with the four beams 42 respectively, wherein the four beams 48 aredistributed evenly around the circular plate 44, so that four identicalopenings 480 each having a shape similar to a square, are definedbetween the circular plate 44 and the four beams 42, 48. A hollow,tubular body 46 extends downwardly and perpendicularly from a bottomface of the circular plate 44, thereby to form a cylindrical space 460together with the circular plate 44. The tubular body 46 has an exteriordiameter less than a diameter of the cavity 320 in the hub 32, and aheight larger than that of the cavity 320, whereby the tubular body 46can be partly accommodated in the cavity 320 with its top portionlocated beyond the hub 32. Four locking feet 420 are formed downwardlyand perpendicularly from four corners of the cover 40 respectivelycorresponding to the four threaded holes 1420 of the frame 10. The cover40 is fixed on the frame 10 by fitting the four locking feet 420 intothe four threaded holes 1420 of the frame 10 respectively, and puttingthe tubular body 46 into the cavity 320 of the hub 32 with a gap definedbetween the circular plate 44 and a top face of the shaft 36 forpreventing an interference from occurring between the shaft 36 and thecover 40. When the fan is assembled completely, the circular plate 44,the tubular body 46, the pair of bearings 50, 60, the hub 32, themagnetic sleeve 38, the hollow tube 124, and the collar 122 would becoaxial with each other.

The upper bearing 60 of the pair of bearings 50, 60 is installed intothe cylindrical space 460 of the cover 40 with its top face contactingthe bottom face of the circular plate 44 securely, its outer facecontacting an inner face of the tubular body 46 of the cover 40, and itsinner face contacting an outer face of the upper portion of the shaft36, whereby the upper portion of the shaft 36 is confined to beprevented from a vibration when the rotor 30 is in rotation.

In use, when an electric power is given to the cooling fan, the coils 24of the stator 20 generates the alternating magnet field that interactswith the magnetic sleeve 38 of the rotor 30, thereby driving the rotor30 to rotate around the shaft 36 in a high speed. Due to the lowerportion and the upper portion of the shaft 36 being supported by thelower one 50 and the upper bearing 60 of the pair of bearings 50, 60,respectively, vibrations caused by unsymmetric forces acting on two endsof the shaft 36 can be prevented. Therefore, the cooling fan can operatein a stable condition without noise generated, and the lifetime of thecooling fan is prolonged accordingly.

It is believed that the present invention and its advantages will beunderstood from the foregoing description, and it will be apparent thatvarious changes may be made thereto without departing from the spiritand scope of the invention or sacrificing all of its materialadvantages, the examples hereinbefore described merely being preferredor exemplary embodiments of the invention.

1. A cooling fan adapted for cooling a heat source, comprising: a frame;a lower bearing received in the frame; a stator attached in the frameand surrounding the lower bearing; a rotor installed in the frame, therotor comprising: a hub enclosing the stator; a plurality of bladesextending outwardly and radially from the hub; and a shaft extendingthrough the hub with a lower portion of the shaft being inserted intothe lower bearing; a cover fixed on the frame to cover the rotor; and anupper bearing received in the cover to accommodate an upper portion ofthe shaft therein, wherein when the cooling fan is in operation,supports respectively provided by the lower bearing to the lower portionof the shaft, and the upper portion to the upper portion of the shaftcooperatively prevent the shaft from vibration.
 2. The cooling fan asclaimed in claim 1, wherein the cover comprises a plurality of beamsconnecting with each other to define an opening, a plate surrounded bythe plurality of beams, and a plurality of additional beamsinterconnecting the plate and the plurality of beams, the plurality ofbeams being secured on the frame to fix the cover on the frame.
 3. Thecooling fan as claimed in claim 2, wherein cover comprises four beamsand four additional beams, the four additional beams dividing theopening into four identical areas each having a shape similar to asquare.
 4. The cooling fan as claimed in claim 2, wherein the coverfurther comprises a tubular body extending downwardly from the plate,the upper bearing being received in the tubular body.
 5. The cooling fanas claimed in claim 4, wherein the hub of the rotor comprises a diskhaving a central area concaved downwardly to form a cavity therein, andan annular flange extending downwardly from a periphery of the disk, thedisk of the hub being in alignment with the plate of the cover.
 6. Thecooling as claimed in claim 5, wherein the tubular body of the cover hasan exterior diameter less than a diameter of the cavity of the hub, anda height larger than that of the cavity, the tubular body being partlyreceived in the cavity of the hub.
 7. The cooling fan as claimed inclaim 5, wherein the upper portion of the shaft is located above thedisk and partly exposed within the cavity of the hub, and the lowerportion of the shaft is located below the disk.
 8. The cooling fan asclaimed in claim 5, wherein the frame comprises a lower plate, an upperplate connecting the plurality of beams of the cover thereon, and anannular sidewall interconnecting the lower plate and the upper plate, athrough hole being defined through the lower plate and the upper platefor receiving the stator and the rotor therein.
 9. The cooling fan asclaimed in claim 8, wherein the frame further comprises a collar formedin a center of the through hole with a plurality of ribs connecting thecollar to the annular sidewall of the frame, the collar being alignmentwith the disk of the hub.
 10. The cooling fan as claimed in claim 9,wherein a hollow tube extends upwardly from the collar of the frame withthe stator disposed therearound, the lower bearing being received in thehollow tube for accommodating the lower portion of the lower bearingtherein.
 11. A cooling fan adapted for dissipating heat from a heatsource, comprising: a frame; a stator mounted in the frame, the statorhaving a plurality of coils for performing a magnet field when given analternating current; an impeller disposed in the frame, the impellerhaving a magnetic sleeve for being repulsed or attracted by the magnetfield to rotate; a cover secured on the frame to sandwich the stator andthe impeller between the cover and the frame; a first bearing beingreceived in the cover; a second bearing being received in the frame; anda shaft extending through the impeller, the shaft having an upperportion being inserted into the first bearing, and a lower portion beinginserted into the second bearing, thus the shaft can be supported at twoends thereof by the first bearing and the second bearing respectively.12. The cooling fan as described in claim 11, wherein the impeller has acentral area concaved downwardly to form a cavity, the upper portion ofthe shaft being exposed within the central area of the impeller to bereceived in the first bearing.
 13. The cooling fan as described in claim12, wherein the cover comprises a rectangular, annular bracket, acircular plate in a center of the cover, a plurality of beams connectingthe circular plate with the rectangular, annular bracket to define fouropenings in the cover, and a tubular body extending downwardly from thecircular plate and having a lower portion partly received in the cavityof the impeller.
 14. The cooling fan as described in claim 13, whereinthe first bearing is received in the tubular body of the cover tosupport the upper portion of the shaft, which is spaced a distance fromthe circular plate of the cover for preventing an interference betweenthe shaft and the cover.
 15. The cooling fan as described in claim 14,wherein the frame has a hollow tube formed at a lower portion thereofwith the second bearing received therein, the hollow tube beingsurrounded by the stator that is surrounded by the magnetic sleeve ofthe impeller.
 16. The cooling fan as described in claim 15, wherein thefirst bearing, the second bearing, the circular plate of the cover, theimpeller, and the hollow tube of the frame are coaxial with each other.